<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    header {
      height: 50px;
      background-color: #21202e;
    }
  </style>
</head>
<body>
  <!-- page.png这张图片不要上传 -->
  <header>

  </header>
</body>
</html>